Belfast Lough is a large, intertidal sea inlet on the east coast of Northern Ireland. At its head is the city and port of Belfast, which sits at the mouth of the River Lagan. The lough opens into the North Channel and connects Belfast to the Irish Sea.

Belfast Harbour is a major maritime hub in Belfast, Northern Ireland, handling 67% of Northern Ireland's seaborne trade and about 25% of the maritime trade of the entire island of Ireland. It is a vital gateway for raw materials, exports and consumer goods, and is also Northern Ireland's leading logistics and distribution hub.